Nasa’s first spending for the platform will be for power and propulsion elements early next year, followed by habitation components, Associate Administrator William Gerstenmaier said on Thursday at the Space Symposium conference in Colorado Springs, Colorado. They will probably be launched moonward, in that order, starting in 2022.

The platform should be orbiting the moon in 2025, said Gerstenmaier, a 41-year Nasa veteran who oversees human exploration and operations. It will carry a four-astronaut crew on 30-day missions, he said.

The gateway would also further Nasa’s goal of another human landing on the moon and will help determine whether water near the surface could be used to manufacture propellant for deep-space missions. The moon’s gravity could also help a spacecraft reduce the blistering speeds used for six-month voyages back and forth to Mars, thus easing re-entry to Earth’s atmosphere.

“We want to understand orbital mechanics around the moon” a little better, far from the Earth’s deep gravity well, he said. “Doing things in this region, where gravity isn’t such a big driver … is a different way of operating.”

In November, Nasa selected five companies to study a high-power solar electric propulsion system to use in deep-space missions, including the lunar platform. Future human missions will require a power system that has triple the capability of current designs.

Trips to the gateway will be on the Orion, a spacecraft being built by Lockheed Martin, with the service module supplied by the European Space Agency.

The Orion’s first flight, without crew, is scheduled for next year. The craft will serve as the command deck when it’s docked with the platform.

The lunar platform is based on current Nasa budgets and “doesn’t require a huge new influx of funding”, Gernstenmaier said. “It’s got fiscal realism, and it’s also adaptable. It can adapt to commercial partners. It’s not a rigid programme of one mission following another. As long as we view the moon as a stepping stone and not an end goal, I think we’re OK.”